Brain inflammation plays a critical role in the pathophysiology of brain diseases of high prevalence and economic impact, such as major depression, schizophrenia, post traumatic stress disorder, Parkinson’s and Alzheimer’s disease and traumatic brain injury. Our results demonstrate that systemic administration of the centrally acting Angiotensin II AT1 receptor blocker candesartan to normotensive rats decreases the acute brain inflammatory response to administration of the bacterial endotoxin lipopolysaccharide, a model of brain inflammation. The broad anti-inflammatory effects of candesartan were seen across the entire inflammatory cascade, including decreased production and release to the circulation of centrally acting pro-inflammatory cytokines, repression of nuclear transcription factors activation in the brain, reduction of gene expression of brain pro-inflammatory cytokines, cytokine and prostanoid receptors, adhesion molecules, pro-inflammatory inducible enzymes, and reduced microglia activation. These effects are widespread, occurring not only in well-known brain target areas for circulating pro-inflammatory factors and lipopolysaccharide, i.e. hypothalamic paraventricular nucleus and the subfornical organ, but also in the prefrontal cortex, hippocampus and amygdala. Candesartan reduced the associated anorexic effects, and ameliorated associated body weight loss and anxiety. Direct anti-inflammatory effects of candesartan were also documented in cultured rat microglia, cerebellar granule cells and cerebral microvascular endothelial cells. AT1 receptor blockers are widely used in the treatment of hypertension and stroke, and their anti-inflammatory effects contribute to reduce renal and cardiac failure. Our results indicate that these compounds may offer a novel and safe therapeutic approach for the treatment of brain disorders.

SUMMARYPoor adaptation to stress, alterations in cerebrovascular function and excessive brain inflammation play critical roles in the pathophysiology of many psychiatric and neurological disorders such as major depression, schizophrenia, post traumatic stress disorder, Parkinson's and Alzheimer's diseases and traumatic brain injury. Treatment for these highly prevalent and devastating conditions is at present very limited and many times inefficient, and the search for novel therapeutic options is of major importance. Recently, attention has been focused on the role of a brain regulatory peptide, Angiotensin II, and in the translational value of the blockade of its physiological AT 1 receptors. In addition to its well-known cardiovascular effects, Angiotensin II, through AT 1 receptor stimulation, is a pleiotropic brain modulatory factor involved in the control of the reaction to stress, in the regulation of cerebrovascular flow and the response to inflammation. Excessive brain AT 1 receptor activity is associated with exaggerated sympathetic and hormonal response to stress, vulnerability to cerebrovascular ischemia and brain inflammation, processes leading to neuronal injury. In animal models, inhibition of brain AT 1 receptor activity with systemically administered Angiotensin II receptor blockers is neuroprotective; it reduces exaggerated stress responses and anxiety, prevents stress-induced gastric ulcerations, decreases vulnerability to ischemia and stroke, reverses chronic cerebrovascular inflammation, and reduces acute inflammatory responses produced by bacterial endotoxin. These effects protect neurons from injury and contribute to increase the lifespan. Angiotensin II receptor blockers are compounds with a good margin of safety widely used in the treatment of hypertension and their anti-inflammatory and vascular protective effects contribute to reduce renal and cardiovascular failure. Inhibition of brain AT 1 receptors in humans is also neuroprotective, reducing the incidence of stroke, improving cognition and decreasing the progression of Alzheimer's disease. Blockade of AT 1 receptors offers a novel and safe therapeutic approach for the treatment of illnesses of increasing prevalence and socioeconomic impact, such as mood disorders and neurodegenerative diseases of the brain.

Long-term pretreatment with an angiotensin II AT 1 antagonist blocks angiotensin II effects in brain and peripheral organs and abolishes the sympathoadrenal and hypothalamic-pituitary-adrenal responses to isolation stress. We determined whether AT 1 receptors were also important for the stress response of higher regulatory centers. We studied angiotensin II and corticotropin-releasing factor (CRF) receptors and benzodiazepine binding sites in brains of Wistar Hannover rats. Animals were pretreated for 13 days with vehicle or a central and peripheral AT 1 antagonist (candesartan, 0.5 mg/kg/day) via osmotic minipumps followed by 24 h of isolation in metabolic cages, or kept grouped throughout the study (grouped controls). In another study, we determined the influence of a similar treatment with candesartan on performance in an elevated plus-maze. AT 1 receptor blockade prevented the isolation-induced increase in brain AT 1 receptors and decrease in AT 2 binding in the locus coeruleus. AT 1 receptor antagonism also prevented the increase in tyrosine hydroxylase mRNA in the locus coeruleus. Pretreatment with the AT 1 receptor antagonist completely prevented the decrease in cortical CRF 1 receptor and benzodiazepine binding produced by isolation stress. In addition, pretreatment with candesartan increased the time spent in and the number of entries to open arms of the elevated plus-maze, measure of decreased anxiety. Our results implicate a modulation of upstream neurotransmission processes regulating cortical CRF 1 receptors and the GABA A complex as molecular mechanisms responsible for the anti-anxiety effect of centrally acting AT 1 receptor antagonists. We propose that AT 1 receptor antagonists can be considered as compounds with possible therapeutic anti-stress and anti-anxiety properties.